Dynamic multi-purpose compositions for the removal of photoresists and method for its use

ABSTRACT

Improved dry stripper solutions for removing one, two or more photoresist layers from substrates are provided. The stripper solutions comprise dimethyl sulfoxide, a quaternary ammonium hydroxide, and an alkanolamine, a secondary solvent, and less than about 3 wt. % water. Methods for the preparation and use of the improved dry stripping solutions are additionally provided.

This application is a continuation of U.S. application Ser. No.12/091,808 filed on Oct. 24, 2006, which is a Continuation-In-Part ofU.S. application Ser. No. 11/260,912 filed on Oct. 28, 2005, which areboth incorporated fully herein by reference.

The present disclosure relates generally to compositions having theability to effectively remove photoresists from substrates and methodsfor their use. The compositions disclosed are stripper solutions for theremoval of photoresists that have the ability to remain liquid attemperatures below normal room temperature and temperatures frequentlyencountered in transit and warehousing and additionally haveadvantageous loading capacities for the photoresist materials that areremoved. Stripper solutions having reduced water content have provenparticularly effective in cleanly removing photoresists, providing lowcopper etch rates, and increasing the solubility of photoresists in thestripper solution as evidenced by lower particle counts.

SUMMARY

In broad terms, a first aspect of the present disclosure provides for aphotoresist stripper solution for effectively removing or stripping aphotoresist from a substrate, having particularly high loadingcapacities for the resist material, and the ability to remain a liquidwhen subjected to temperatures below normal room temperature that aretypically encountered in transit, warehousing and in use in somemanufacturing facilities. The compositions according to this presentdisclosure typically remain liquid to temperatures as low as about −20°C. to about +15° C. The compositions according to the present disclosuretypically contain dimethyl sulfoxide (DMSO), a quaternary ammoniumhydroxide, and an alkanolamine. One preferred embodiment contains fromabout 20% to about 90% dimethyl sulfoxide, from about 1% to about 7% ofa quaternary ammonium hydroxide, and from about 1% to about 75% of analkanolamine having at least two carbon atoms, at least one aminosubstituent and at least one hydroxyl substituent, the amino andhydroxyl substituents attached to two different carbon atoms. Thepreferred quaternary groups are (C₁-C₈) alkyl, arylalkyl andcombinations thereof. A particularly preferred quaternary ammoniumhydroxide is tetramethyammonium hydroxide. Particularly preferred1,2-alkanolamines include compounds of the formula:

where R¹ can be H, C₁-C₄, alkyl, or C₁-C₄ alkylamino. For particularlypreferred alkanol amines of formula I, R¹ is H or CH₂CH₂NH₂. A furtherembodiment according to this present disclosure contains an additionalor secondary solvent. Preferred secondary solvents include glycols,glycol ethers and the like.

A second aspect of the present disclosure provides for methods of usingthe novel stripper solutions described above to remove photoresist andrelated polymeric materials from a substrate. A photoresist can beremoved from a selected substrate having a photoresist thereon bycontacting the substrate with a stripping solution for a time sufficientto remove the desired amount of photoresist, by removing the substratefrom the stripping solution, rinsing the stripping solution from thesubstrate with a solvent and drying the substrate.

A third aspect of the present disclosure includes electronic devicesmanufactured by the novel method disclosed.

A fourth aspect of the present disclosure includes preferred strippersolutions containing dimethyl sulfoxide, a quaternary ammoniumhydroxide, an alkanolamine, an optional secondary solvent with reducedamounts of water. The preferred solutions have a dryness coefficient ofat least about 1 and more preferred solutions having a drynesscoefficient of at least about 1.8, where the dryness coefficient (DC) isdefined by the following equation:

${D\; C} = \frac{{mass}\mspace{14mu} {of}\mspace{14mu} {{base}/{mass}}\mspace{14mu} {of}\mspace{14mu} {solution}\mspace{14mu} {tested}}{{mass}\mspace{14mu} {of}\mspace{14mu} {{water}/{mass}}\mspace{14mu} {of}\mspace{14mu} {solution}\mspace{14mu} {tested}}$

A fifth aspect of the present disclosure includes a method for removinga photoresist from a substrate with the new dry stripper solution. Themethod involves selecting a substrate having a photoresist deposited onit, contacting the substrate including the photoresist with a strippersolution that contains dimethyl sulfoxide, a quaternary ammoniumhydroxide, an alkanolamine, an optional secondary solvent wherein thestripper solution has a dryness coefficient of at least about 1,removing the substrate from contact with the stripper solution andrinsing the stripper solution from the substrate.

A sixth aspect of the present disclosure includes an electronic deviceprepared in part by the method described above.

A seventh aspect of the present disclosure includes a method forproviding a dry composition that includes dimethyl sulfoxide, aquaternary ammonium hydroxide, an alkanolamine, an optional secondarysolvent wherein the solution has a dryness coefficient of at least about1.

An eighth aspect of the present disclosure includes a method forobtaining a quaternary ammonium hydroxide having reduced water contentby forming a solution of the quaternary ammonium hydroxide, unwantedwater and a sacrificial solvent and subjecting the solution to reducedpressure with slight warming. During the treatment a portion ofsacrificial solvent and water are removed. During the process excessiveheating should be avoided to prevent decomposition of the hydroxide. Theaddition and removal of the sacrificial solvent with water can berepeated as necessary until the water content is sufficiently reduced.

A ninth aspect of the present disclosure includes a method formaintaining a low water content for a stripper solution. The methodinvolves selecting a dry stripper solution, establishing contact betweenthe stripper solution and molecular sieves, and maintaining contact withthe sieves until the stripper solution is utilized. This method isparticularly useful in maintaining the stripper solutions in a dry formfollowing manufacture, during storage and/or shipping and after thesolution's container has been opened.

DESCRIPTION

For the purposes of promoting an understanding of what is claimed,references will now be made to the embodiments illustrated and specificlanguage will be used to describe the same. It will nevertheless beunderstood that no limitation of the scope of what is claimed is therebyintended, such alterations and further modifications and such furtherapplications of the principles thereof as illustrated therein beingcontemplated as would normally occur to one skilled in the art to whichthe disclosure relates.

The compositions according to this present disclosure include dimethylsulfoxide (DMSO), a quaternary ammonium hydroxide, and an alkanolamine.Preferred alkanol amines having at least two carbon atoms, at least oneamino substituent and at least one hydroxyl substituent, the amino andhydroxyl substituents attached to two different carbon atoms. Preferredquaternary substituents include (C₁-C₈) alkyl, benzyl and combinationsthereof. Preferred compositions have a freezing point of less than about−20° C. up to about +15° C. and a loading capacity of from about 15cm³/liter up to about 90 cm³/liter. For the dry stripper solutions,preferred quaternary substituents include C₁-C₄ alkyl, arylalkyl orcombinations thereof.

Formulations having increased levels of an alkanolamine are particularlynoncorrosive to carbon steel are less injurious to typical wastetreatments systems and auxiliary equipment than other strippersolutions. Particularly preferred compositions contain 1,2-alkanolamineshaving the formula:

where R¹ is hydrogen, (C₁-C₄) alkyl, or (C₁-C₄) alkylamino. Somepreferred formulations additionally contain a secondary solvent.Particularly preferred formulations contain from about 2% to about 75%of a secondary solvent. Particularly useful secondary solvents includeglycols and their alkyl or aryl ethers described in more detail below.The preferred formulations have freezing points sufficiently below 25°C. to minimize solidification during transportation and warehousing.More preferred formulations have freezing points below about 15° C.Because the preferred stripper solutions remain liquid at lowtemperatures, the need to liquefy solidified drums of stripper solutionreceived during cold weather or stored in unheated warehouses before thesolution can be used is eliminated or minimized. The use of drum heatersto melt solidified stripper solution is time consuming, requires extrahandling and can result in incomplete melting and modification of themelted solution's composition.

Additionally, compositions according to the present disclosure displayhigh loading capacities enabling the composition to remove higher levelsof photoresists without the precipitation of solids. The loadingcapacity is defined as the number of cm³ of photoresist or bilayermaterial that can be removed for each liter of stripper solution beforematerial is re-deposited on the wafer or before residue remains on thewafer. For example, if 20 liters of a stripper solution can remove 300cm³ of photoresist before either redepositon occurs or residue remainson the wafer, the loading capacity is 300 cm³/20 liters=15 cm²/liter

The compositions typically contain about 55% to about 95% solvent, allor most of which is DMSO and from about 2% to about 10% of thequaternary ammonium hydroxide. Preferred quaternary substituents include(C₁-C₈)alkyl, benzyl and combinations thereof. When used, a secondarysolvent typically comprises from about 2% to about 35% of thecomposition. The stripping formulations can also contain an optionalsurfactant, typically at levels in the range of about 0.01% to about 3%.Suitable levels of the required alkanolamine can range from about 2% toabout 75% of the composition. Because some of the stripper solution'scomponents can be provided as aqueous solutions, the composition canoptionally contain small amounts of water. All %'s provided herein areweight per cents.

Preferred alkanolamines have at least two carbon atoms and have theamino and hydroxyl substituents on different carbon atoms. Suitablealkanolamines include, but are not limited to, ethanolamine,N-methylethanolamine, N-ethylethanolamine, N-propylethanolamine,N-butylethanolamine, diethanolamine, triethanolamine,N-methyldiethanolamine, N-ethyldiethanolamine, isopropanolamine,diisopropanolamine, triisopropanolamine, N-methylisopropanolamine,N-ethylisopropanolamine, N-propylisopropanolamine, 2-aminopropane-1-ol,N-methyl-2-aminopropane-1-ol, N-ethyl-2-aminopropane-1-ol,1-aminopropane-3-ol, N-methyl-1-aminopropane-3-ol,N-ethyl-1-aminopropane-3-ol, 1-aminobutane-2-ol,N-methyl-1-aminobutane-2-ol, N-ethyl-1-aminobutane-2-ol,2-aminobutane-1-ol, N-methyl-2-aminobutane-1-ol,N-ethyl-2-aminobutane-1-ol, 3-aminobutane-1-ol,N-methyl-3-aminobutane-1-ol, N-ethyl-3-aminobutane-1-ol,1-aminobutane-4-ol, N-methyl-1-aminobutane-4-ol,N-ethyl-1-aminobutane-4-ol, 1-amino-2-methylpropane-2-ol,2-amino-2-methylpropane-1-ol, 1-aminopentane-4-ol,2-amino-4-methylpentane-1-ol, 2-aminohexane-1-ol, 3-aminoheptane-4-ol,1-aminooctane-2-ol, 5-aminooctane-4-ol, 1-aminopropane-2,3-diol,2-aminopropane-1,3-diol, tris(oxymethyl)aminomethane,1,2-diaminopropane-3-ol, 1,3-diaminopropane-2-ol, and2-(2-aminoethoxy)ethanol.

Appropriate glycol ether solvents include, but are not limited to,ethylene glycol monomethyl ether, ethylene glycol monoethyl ether,ethylene glycol monobutyl ether, ethylene glycol dimethyl ether,ethylene glycol diethyl ether, diethylene glycol monomethyl ether,diethylene glycol monoethyl ether, diethylene glycol monopropyl ether,diethylene glycol monoisopropyl ether, diethylene glycol monobutylether, diethylene glycol monoisobutyl ether, diethylene glycolmonobenzyl ether, diethylene glycol diethyl ether, triethylene glycolmonomethyl ether, triethylene glycol dimethyl ether, polyethylene glycolmonomethyl ether, diethylene glycol methyl ethyl ether, triethyleneglycol, ethylene glycol monomethyl ether acetate, ethylene, glycolmonoethyl acetate, propylene glycol monomethyl ether, propylene glycoldimethyl ether, propylene glycol monobutyl ether, dipropyelene glycolmonomethyl ether, dipropylene glycol monopropyl ether, dipropyleneglycol monoisopropyl ether, dipropylene glycol monobutyl ether,dipropylene glycol dimethyl ether, dipropylene glycol dipropyl ether,dipropylene glycol diisopropyl ether, tripropylene glycol andtripropylene glycol monomethyl ether, 1-methoxy-2-butanol,2-methoxy-1-butanol, 2-methoxy-2-methyl-2-butanol,3-methoxy-3-methyl-1-butanol, dioxane, trioxane, 1,1-dimethoxyethane,tetrahydrofuran, crown ethers and the like.

The compositions can also optionally contain one or more corrosioninhibitors. Suitable corrosion inhibitors include, but are not limitedto, aromatic hydroxyl compounds such as catechol; alkylcatechols such asmethylcatechol, ethylcatechol and t-butylcatechol, phenols andpyrogallol; aromatic triazoles such as benzotriazole;alkylbenzotriazoles; carboxylic acids such as formic acid, acetic acid,propionic acid, butyric acid, isobutyric acid, oxalic acid, malonicacid, succinic acid, glutatic acid, maleic acid, fumaric acid, benzoicacid, phtahlic acid, 1,2,3-benzenetricarboxylic acid, glycolic acid,lactic acid, malic acid, citric acid, acetic anhydride, phthalicanhydride, maleic anhydride, succinic anhydride, salicylic acid, gallicacid, and gallic acid esters such as methyl gallate and propyl gallate;organic salts of carboxyl containing organic containing compoundsdescribed above, basic substances such as ethanolamine, trimethylamine,diethylamine and pyridines, such as 2-aminopyridine, and the like, andchelate compounds such as phosphoric acid-based chelate compoundsincluding 1,2-propanediaminetetramethylene phosphonic acid andhydroxyethane phosphonic acid, carboxylic acid-based chelate compoundssuch as ethylenediaminetetraacetic acid, and its sodium and ammoniumsalts, dihydroxyethylglycine and nitrilotriacetic acid, amine-basedchelate compounds such as bipyridine, tetraphenylporphyrin andphenanthroline, and oxime-based chelate compounds such asdimethylglyoxime and diphenylglyoxime. A single corrosion inhibitor maybe used ox a combination of corrosion inhibitors may be used. Corrosioninhibitors have proven useful at levels ranging from about 1 ppm toabout 10%.

Preferred optional surfactants have included fluorosurfactants. Oneexample of a preferred fluorosurfactant is DuPont FSO (fluorinatedtelomere B monoether with polyethylene glycol (50%), ethylene glycol(25%), 1,4-dioxane (<0.1%), water 25%).

Preferred temperatures of at least 50° C. are preferred for contactingthe substrate whereas for a majority of applications, temperatures offrom about 50° C. to about 75° C. are more preferred. For particularapplications where the substrate is either sensitive or longer removaltimes are required, lower contacting temperatures are appropriate. Forexample, when reworking substrates, it may be appropriate to maintainthe stripper solution at a temperature of at least 20° C. for a longertime to remove the photoresist and avoid damaging to the substrate. Iflonger contact times are required for complete resist removal, placing ablanket of dry nitrogen over the stripper solution can reduce wateruptake from the atmosphere and maintain the dry stripper solution'simproved performance.

When immersing a substrate, agitation of the composition additionallyfacilitates photoresist removal. Agitation can be effected by mechanicalstirring, circulating, or by bubbling an inert gas through thecomposition. Upon removal of the desired amount of photoresist, thesubstrate is removed from contact with the stripper solution and rinsedwith water or an alcohol. DI water is a preferred form of water andisopropanol is a preferred alcohol. For substrates having componentssubject to oxidation, rinsing is preferably done under an inertatmosphere. The preferred stripper solutions according to the presentdisclosure have improved loading capacities for photoresist materialscompared to current commercial products and are able to process a largernumber of substrates with a given volume of stripper solution.

The stripper solutions provided in this disclosure can be used to removepolymeric resist materials present in a single layer or certain types ofbilayer resists. For example, bilayer resists typically have either afirst inorganic layer covered by a second polymeric layer or can havetwo polymeric layers. Utilizing the methods taught below, a single layerof polymeric resist can be effectively removed from a standard waferhaving a single polymer layer. The same methods can also be used toremove a single polymer layer from a wafer having a bilayer composed ofa first inorganic layer and a second or outer polymer layer. Finally,two polymer layers can be effectively removed from a wafer having abilayer composed of two polymeric layers. The new dry stripper solutionscan be used to remove one, two or more resist layers.

The preferred dry stripper solutions contain dimethyl sulfoxide,quaternary ammonium hydroxide, an alkanolamine, an optional secondarysolvent and less than about 3 wt. % of water. Preferred secondarysolvents are glycol ethers. More preferred dry stripper solutionscontain dimethyl sulfoxide, a quaternary ammonium hydroxide, analkanolamine, a glycol ether solvent and a dryness coefficient of atleast about 1.8

Use of the dry photoresist stripper solution is similar to thatdescribed above for stripper solutions having a low freezing point.However, it is helpful to maintain the stripper solution in a dry formprior to use and to minimize water uptake during its use by maintaininga generally dry environment in the area involved with resist removal.Stripper solutions can be maintained in a dry state by maintainingcontact between the stripper solution and active molecular sieves duringstorage, transit and after opening a container prior to its use.

The dry stripper solutions described herein should be prepared from drycomponents to the extent possible. Because quaternary ammoniumhydroxides are hygroscopic and are generally available as aqueoussolutions or their hydrates, water contained in the solution orassociated with the hydrate must generally be removed to provide a drystripper solution having a dryness coefficient of at least about 1.Efforts to dry quaternary ammonium hydroxides at elevated temperaturesand to a dry state generally results in decomposition of the hydroxide.It has surprisingly been found that quaternary ammonium hydroxides in avolatile solvent can be pre-dried to give a solvent wet paste havingreduced water content without decomposition. A dry stripper solutioncontaining a quaternary ammonium hydroxide can be prepared by pre-dryingthe quaternary ammonium hydroxide and combining it with othersubstantially dry components to maintain a low water content or bysubsequently drying an initially formed wet stripper solution formedfrom water-containing components.

A pre-dried form of a quaternary ammonium hydroxide can be obtained bysubjecting a hydrated or otherwise wet form of a quaternary ammoniumhydroxide to a reduced pressure with very slight warming. Water removalmay be facilitated by dissolving the quaternary ammonium hydroxide in asolvent such as an alcohol prior to subjecting the hydroxide to reducedpressure. Based on work carried out thus far, a preferred alcohol ismethanol. During this treatment a substantial portion of the water andalcohol are removed to provide an alcohol wet paste of the quaternaryammonium hydroxide. Depending on the level of dryness desired,additional dry alcohol can be added to the initially treated hydroxideand the treatment at reduced pressure repeated one or more times.Treatments can be carried out at pressures of from about 0.001 to about30 mmhg and at temperatures of up to at least about 35° C. withoutsubstantial decomposition of the quaternary ammonium hydroxide. Morepreferred treatments can be carried out at pressures of from about 0.01to about 10 mmhg.

For wet formulations with or without a secondary solvent, drying can becarded out on the stripper solution after the addition of all componentsby contacting the stripper solution with a solid drying agent, such asfor example, molecular sieves, calcium hydride, calcium sulfate or acombination of drying agents. A preferred drying agent is an activated3A or 4A molecular sieve. For dry stripper solutions containing asecondary solvent, it is preferred to combine the quaternary ammoniumhydroxide (and any other wet components), contact the resulting solutionwith an active drying agent such as molecular sieves, separate the drysolution from the spent drying agent and add any remaining drycomponents to the dry solution. Contact with the molecular sieves orother solid drying agent can be by any known method, such as slurryingthe solution with drying agent and filtering the dry slurry. Similarly,any of the wet solutions described above can be dried by passing the wetsolution through pelletized activated molecular sieves or other dryingagent in a column. Suitable molecular sieves include type 3A, 4A and 5Asieves.

Molecular sieves are also a preferred drying agent or desiccant tomaintain the stripper solution in a dry state. The pellet form is mostpreferred because it allows removal of the dry stripper solution bysimple decantation. However, for applications in which decantation doesnot provide an adequate separation, molecular sieve, whether powder orpellets can be incorporated into a “tea bag” arrangement that will allowequilibrium with the solution, but not allow any sieve particles tocontaminate the solution. Dry stripper solutions containing molecularsieves can be maintained in a dry state for extended periods of timeafter a container has been opened, depending on the amount of molecularsieves included with the stripper solution, the surrounding humidity andthe amount of time the container is open.

Examples 1-13

The reactants listed in Table I were separately combined with stirringto give each of the 13 homogeneous stripper solutions. The freezingpoints were determined and are also provided in Table 1. Thecompositions of Examples 1-13 can optionally be formulated without asurfactant and formulated to include a corrosion inhibitor.

TABLE I Exam- Freezing Dryness ple Formulation* Point, ° C. Coefficient1 85.8 g DMSO (85.8%) +13.2 1 6.0 g Diethyleneglycol monomethyl ether(6.0%) 2.7 g Aminoethylethanolamine (2.7%) 2.75 g Tetramethylammoniumhydroxide (2.75%) 2.75 g water (2.75%) 2 61 g DMSO (61%) −2.5 1 35 gMonoethanolamine (35%) 2 g Tetramethylammonium hydroxide (2%) 2 g water(2%) 3 51.5 g DMSO (51.5%) −7.4 1 35 g Diethylene glycol monomethylether (35%) 11.3 g Aminoethylethanolamine (11.3%) 1.1 gTetramethylammonium hydroxide (1.1%) 1.1 g water (1.1%) 4 71 g DMSO(71%) +5.3 1 27.4 g Monoethanolamine (27.4%) 0.8 g Tetramethylammoniumhydroxide (0.8%) 0.8 g water (0.8%) 5 27.4 g DMSO (27.4%) +0.4 1 71 gMonoethanolamine (71%) 0.8 g Tetramethylammonium hydroxide (0.8%) 0.8 gwater (0.8%) 6 86 g DMSO (86.4%) +7.7 0.7 6 g Diethylene glycolmonomethyl ether (6%) 2.7 g Aminoethylethanolamine (2.7%) 2 gBenzyltrimethylammonium hydroxide (2%) 3 g water (3%) 7 86 g DMSO(82.1%) −4.6 0.25 6 g Diethylene glycol monomethyl ether (5.7%) 2.7 gAminoethylethanolamine (2.6%) 2 g Diethyldimethylammonium hydroxide(1.9%) 8 g water (7.7%) 8 86 g DMSO (82.1%) −5.5 0.25 6 g Diethyleneglycol monomethyl ether (5.7%) 2.7 Aminoethylethanolamine (2.6%) 2 gMethyltriethylammonium hydroxide (1.9%) 8 g water (7.7%) 9 86 g DMSO(87.5%) +8.4 0.8 6 g Diethylene glycol monomethyl ether (6.1%) 2.7 gAminoethylethanolamine (2.8%) 1.6 g Tetrabutylammonium hydroxide (1.6%)2 g water (2%) 10 63 g DMSO (61.2%) −6.3 0.7 35 g Monoethanolamine (34%)2 g Benzyltrimethylammonium hydroxide (1.9%) 3 g water (2.9%) 11 63 gDMSO (58.3%) <−20 0.25 35 g Monoethanolamine (32.4%) 2 gDiethyldimethylammonium hydroxide (1.9%) 8 g water (7.4%) 12 63 g DMSO(58.3%) <−20 0.25 35 g Monoethanolamine (32.4%) 2 gMethyltriethylammonium hydroxide (1.9%) 8 g water (7.4%) 13 63 g DMSO(62.0%) −6.2 0.8 35 g Monoethanolamine (34.4%) 1.6 g Tetrabutylammoniumhydroxide (1.6%) 2 g water (2%) *Each formulation additionally containedan optional 0.03 g of DuPont FSO (fluorinatad telomere B monoether withpolyethylene glycol (50%), ethylene glycol (25%), 1,4-dioxane (<0.1%),water 25%)

Example 14

A silicon wafer having a photoresist thereon is immersed in thestripping solution from Example 1, maintained at a temperature of about70° C. with stilling for from about 30 to about 60 minutes. The wafer isremoved, rinsed with DI water and dried. Examination of the wafer willdemonstrate removal of substantially all of the photoresist. For someapplications, superior results may be obtained by immersing the wafer inthe stripping solution without stirring and/or immersing the wafer forup to 150 minutes. The preferred manner of removing the photoresist froma wafer can readily be determined without undue experimentation. Thismethod can be used to remove a single layer of polymeric photoresist ortwo polymeric layers present in bilayer resists having two polymerlayers.

Example 15

A silicon wafer having a photoresist thereon is mounted in a standardspray device and sprayed with the stripper solution from Example 2,maintained at about 50° C. The spraying can optionally be carried outunder an inert atmosphere or optionally in the presence of an active gassuch as, for example, oxygen, fluorine or silane. The wafer can beremoved periodically and inspected to determine when sufficientphotoresist has been removed. When sufficient photoresist has beenremoved, the wafer can be rinsed with isopropanol and dried. This methodcan be used to remove a single layer of polymeric photoresist or twopolymeric layers present in bilayer resists having two polymer layers.

The methods described in Examples 14 and 15 can be used with thestripper solutions of this disclosure to remove photoresists from wafersconstructed of a variety of materials, including GaAs. Additionally,both positive and negative resists can be removed by both of thesemethods.

The methods described in Examples 14, 15 and 16 can similarly be usedwith the dry stripper solution described herein.

Example 16

The method described in Example 14 was used to remove photoresist fromthe wafers described below in Table II. Twenty liter volumes of threestripper solutions were used until either a residue of photoresistpolymer remained on the wafer or until re-deposition of the polymer orits degradation products onto the wafer occurred, at which point thesolutions loading capacity was reached. With this method the loadingcapacity was determined for the two stripper solutions described inExamples 1 and 2 above and for a comparative example that is generallytypical of current commercial stripper solutions.

TABLE II Wafers Stripped Resist Stripping with 20 L Loading Formula- ofStripper Capacity tion Composition Solution cm³/L From 85.5 g DMSO 150 ×200 mm 18.8 Example 6 g Diethylene glycol wafers with 1 monomethyl ether80 μm 2.7 g Aminoethylethanolamine photoresist 2.75 gTetramethylammonium hydroxide 2.75 g water 0.03 g DuPont FSO surfactantFrom 61 g DMSO 200 × 300 mm 84.8 Example 35 g Monoethanolamine waferswith 2 2 g Tetramethylammonium 120 μm hydroxide photoresist 2 g water0.03 g DuPont FSO surfactant Compara- 74 g n-methylpyrrolidone 25 × 300mm 10.6 tive 24 g 1,2-propanediol wafers with Example 1 gTetramethylammonium 120 μm hydroxide photoresist 1 g water

Example 17

Dimethylsulfoxide (85.5 g), diethyleneglycol monomethyl ether (6.0 g),aminoethylethanolamine (2.7 g) and tetramethylammonium hydroxidepentahydrate (5.5 g) were combined to provide a stripper solutioncontaining about 3 wt. % water and a dryness coefficient of about 0.9.Dissolution of the hydroxide pentahydrate was facilitated by slightlyagitating the mixture. The about 3 wt. % water in the solution camesubstantially from the pentahydrate.

Example 18

Active 3A molecular sieves were added to three different samples of thestripper solution prepared according to the method of Example 17 andmaintained in contact with the stripper solutions for 72 hours atambient temperature. The sieves were removed by filtration and themoisture content of the initial and dried solutions determined by theKarl Fischer method. The dried stripper solutions were stored in closedcontainer. The spent sieves could be dried for reuse or disposed of. Thespecific details for this experiment are tabulated below in Table III.

TABLE III Stripper Solution Sieves % Water Dryness Example (g) (g)Remaining Coefficient 18 (a) 11.4 15.16 2.37 1.13 18 (b) 126.4 25 1.361.99 18 (c) 135.48 45.25 0.78 3.46Varying amounts of calcium hydride, as well as other solid desiccantscan be substituted for molecular sieves in this example to providestripper solutions having similarly reduced levels of water.

Example 19

Three silicon wafers having a negative acrylate polymer-based dry filmphotoresist (120 μm) placed thereon over a copper region were separatelyimmersed in the three dried stripper solutions prepared in Example 18and maintained at 70° C. for 60 minutes. The samples were removed andrinsed with deionized water for one minute. The resulting strippersolutions were analyzed for the number of particles of photoresistsuspended therein utilizing a LiQuilaz SO5 particle analyzer and thecopper etch rate determined for each wafer. The results are tabulated inTable IV provided below. LiQuilaz is a registered trademark of ParticleMeasuring Systems, Inc., 5475 Airport Blvd., Boulder, Colo., 80301.

TABLE IV Mass of Particles/g Stripper Stripper Number of Removedphotoresist Copper Solution Solution Suspended Photoresist removed/gEtch Rate Source (g) Particles (g) solution Å/minute 18 (a) 114.512444.4 0.2428 447.63 <1.0 18 (b) 126.4 9088.4 0.2914 246.74 <1.0 18 (c)135.8 186.8 0.2523 5.46 <1.0Photoresist removal as described above can be carried out attemperatures ranging from about 70° C. to about 80° C. without takingany measures to exclude moisture. However, when photoresist removal iscarried out at lower temperatures, of less than about 70° C., it may behelpful to take measures to minimize the uptake of moisture from theatmosphere. Providing a blanket of dry nitrogen over the strippersolution maintained at less than about 70° C. has proven effective tominimize water uptake by the stripper solution with longer exposures toa moist atmosphere. The ability of the dry stripper solutions describedabove to dissolve larger amounts of photoresists and minimize the numberof particles dispersed in the stripper solutions extends the strippersolutions effective lifetime and reduces overall costs.

Example 20

A 25 wt % solution of tetramethylammonium hydroxide pentahydrate inmethanol was prepared and 40.8 grams of the solution was warmed to about30° C. in a water bath and maintained at a pressure of about 0.01 mmhgfor about 75 minutes. Condensate was collected in a Dewar flask cooledwith liquid nitrogen. After about 75 minutes, the temperature of thewater bath was raised to about 35° C. and maintained at that temperaturefor an additional 105 minutes. A white paste resulted. The vacuum wasbroken and 85.8 g of dry DMSO was added to dissolve the white solidafter which were added 6.0 g of diethyleneglycol monomethyl ether and2.7 g of aminoethylethanolamine to provide a substantially dry versionof the stripper solution described in Example 1, Table I. The drystripper solution's water content was found to be 0.71% by the KarlFischer method and the solution contained less than 1% methanol. Lowerlevels of water can be obtained by adding additional methanol to thewhite paste and maintaining the resulting solution at reduced pressurefor an additional 2 to 5 hours.

Example 21

Appropriate quantities of dry stripper solutions of the type describedin Example 18 are packaged with active molecular sieves to maintain thestripper solutions in a dry condition for longer periods of time. About5 to about 10 grams of active sieves are added for each 100 g ofstripper solution maintained in a closed and sealed container. Molecularsieves in the form of pellets are preferred. However, powdered sievescan be used if removed by filtration prior to use or if small amounts ofparticulate matter do not interfere with use of the dry strippersolution.

While applicant's disclosure has been provided with reference tospecific embodiments above, it will be understood that modifications andalterations in the embodiments disclosed may be made by those practicedin the art without departing from the spirit and scope of the invention.All such modifications and alterations are intended to be covered.

What is claimed is:
 1. A stripper solution for removing a photoresistfrom a substrate comprising: (a) dimethyl sulfoxide; (b) a quaternaryammonium hydroxide; (c) an alkanolamine having at least two carbonatoms, at least one amino substituent and at least one hydroxylsubstituent, the amino and hydroxyl substituents attached to differentcarbon atoms; (d) less than 3 wt % water; and (e) a secondary solvent.2. The solution of claim 1, wherein the quaternary ammonium hydroxidehas substituents that are (C₁-C₈)alkyl, arylalkyl or combinationsthereof.
 3. The solution of claim 2, wherein the dimethyl sulfoxidecomprises from about 20% to about 90% of the composition; the quaternaryammonium hydroxide comprises from about 1% to about 7% of thecomposition; the alkanolamine comprises from about 1% to about 75% ofthe composition.
 4. The solution of claim 1, wherein the alkanolamine isa compound of the formula:

where R¹ is H, CI-C4 alkyl, or C1-C4 alkylamino.
 5. The solution ofclaim 4, wherein R1 is H.
 6. The solution of claim 5, further comprisinga surfactant.
 7. The solution of claim 6, wherein the quaternaryammonium hydroxide is tetramethylammonium hydroxide.
 8. The solution ofclaim 1, additionally comprising 2 to 35% of a secondary solvent.
 9. Thesolution of claim 8, wherein the alkanolamine is:

where R¹ is H, C₁-C₄ alkyl, or C₁-C₄ alkylamino.
 10. The solution ofclaim 10, wherein the secondary solvent is a glycol ether.
 11. Thesolution of claim 10, wherein the glycol ether is diethyleneglycolmonomethyl ether.
 12. The solution of claim 11, wherein RI isCH_(z)CH₂NH₂.
 13. The solution of claim 11, wherein the quaternaryammonium hydroxide is tetramethylammonium hydroxide.
 14. The solution ofclaim 1, wherein the secondary solvent comprises ethylene glycolmonomethyl ether, ethylene glycol monoethyl ether, ethylene glycolmonobutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethylether, diethylene glycol monomethyl ether, diethylene glycol monoethylether, diethylene glycol monopropyl ether, diethylene glycolmonoisopropyl ether, diethylene glycol monobutyl ether, diethyleneglycol monoisobutyl ether, diethylene glycol monobenzyl ether,diethylene glycol diethyl ether, triethylene glycol monomethyl ether,triethylene glycol dimethyl ether, polyethylene glycol monomethyl ether,diethylene glycol methyl ethyl ether, triethylene glycol, ethyleneglycol monomethyl ether acetate, ethylene glycol monoethyl acetate,propylene glycol monomethyl ether, propylene glycol dimethyl ether,propylene glycol monobutyl ether, dipropyelene glycol monomethyl ether,dipropylene glycol monopropyl ether, dipropylene glycol monoisopropylether, dipropylene glycol monobutyl ether, dipropylene glycol dimethylether, dipropylene glycol dipropyl ether, dipropylene glycol diisopropylether, tripropylene glycol and tripropylene glycol monomethyl ether,I-methoxy-2-butanol, 2-methoxy-1-butanol, 2-methoxy-2-methyl-2-butanol,dioxane, trioxane, 1,I-dimethoxyethane, tetrahydrofuran, or crownethers.
 15. The solution of claim 14, wherein the secondary solventcomprises ethylene glycol monomethyl ether, ethylene glycol monobutylether, diethylene glycol monomethyl ether, diethylene glycolmonoisopropyl ether, diethylene glycol monobutyl ether, diethyleneglycol methyl ethyl ether, ethylene glycol monomethyl ether acetate,propylene glycol monomethyl ether, propylene glycol monobutyl ether,dipropyelene glycol monomethyl ether, or dipropylene glycol monobutylether.